Revert "Get rid of custom pretty-printing in rustdoc"

This reverts commit 31375d2.

Author: LeSeulArtichaut

src/librustdoc/clean/mod.rs

@@ -962,7 +962,7 @@ impl<'a> Clean<Arguments> for (&'a [hir::Ty<'a>], hir::BodyId) {
                 .iter()
                 .enumerate()
                 .map(|(i, ty)| Argument {
-                    name: Symbol::intern(&rustc_hir_pretty::param_to_string(&body.params[i])),
+                    name: name_from_pat(&body.params[i].pat),
                     type_: ty.clean(cx),
                 })
                 .collect(),

src/librustdoc/clean/utils.rs

@@ -315,6 +315,25 @@ crate fn strip_path(path: &Path) -> Path {
     Path { global: path.global, res: path.res, segments }
 }
 
+crate fn qpath_to_string(p: &hir::QPath<'_>) -> String {
+    let segments = match *p {
+        hir::QPath::Resolved(_, ref path) => &path.segments,
+        hir::QPath::TypeRelative(_, ref segment) => return segment.ident.to_string(),
+        hir::QPath::LangItem(lang_item, ..) => return lang_item.name().to_string(),
+    };
+
+    let mut s = String::new();
+    for (i, seg) in segments.iter().enumerate() {
+        if i > 0 {
+            s.push_str("::");
+        }
+        if seg.ident.name != kw::PathRoot {
+            s.push_str(&seg.ident.as_str());
+        }
+    }
+    s
+}
+
 crate fn build_deref_target_impls(cx: &DocContext<'_>, items: &[Item], ret: &mut Vec<Item>) {
     let tcx = cx.tcx;
 
@@ -352,6 +371,57 @@ impl ToSource for rustc_span::Span {
     }
 }
 
+crate fn name_from_pat(p: &hir::Pat<'_>) -> Symbol {
+    use rustc_hir::*;
+    debug!("trying to get a name from pattern: {:?}", p);
+
+    Symbol::intern(&match p.kind {
+        PatKind::Wild => return kw::Underscore,
+        PatKind::Binding(_, _, ident, _) => return ident.name,
+        PatKind::TupleStruct(ref p, ..) | PatKind::Path(ref p) => qpath_to_string(p),
+        PatKind::Struct(ref name, ref fields, etc) => format!(
+            "{} {{ {}{} }}",
+            qpath_to_string(name),
+            fields
+                .iter()
+                .map(|fp| format!("{}: {}", fp.ident, name_from_pat(&fp.pat)))
+                .collect::<Vec<String>>()
+                .join(", "),
+            if etc { ", .." } else { "" }
+        ),
+        PatKind::Or(ref pats) => pats
+            .iter()
+            .map(|p| name_from_pat(&**p).to_string())
+            .collect::<Vec<String>>()
+            .join(" | "),
+        PatKind::Tuple(ref elts, _) => format!(
+            "({})",
+            elts.iter()
+                .map(|p| name_from_pat(&**p).to_string())
+                .collect::<Vec<String>>()
+                .join(", ")
+        ),
+        PatKind::Box(ref p) => return name_from_pat(&**p),
+        PatKind::Ref(ref p, _) => return name_from_pat(&**p),
+        PatKind::Lit(..) => {
+            warn!(
+                "tried to get argument name from PatKind::Lit, which is silly in function arguments"
+            );
+            return Symbol::intern("()");
+        }
+        PatKind::Range(..) => panic!(
+            "tried to get argument name from PatKind::Range, \
+             which is not allowed in function arguments"
+        ),
+        PatKind::Slice(ref begin, ref mid, ref end) => {
+            let begin = begin.iter().map(|p| name_from_pat(&**p).to_string());
+            let mid = mid.as_ref().map(|p| format!("..{}", name_from_pat(&**p))).into_iter();
+            let end = end.iter().map(|p| name_from_pat(&**p).to_string());
+            format!("[{}]", begin.chain(mid).chain(end).collect::<Vec<_>>().join(", "))
+        }
+    })
+}
+
 crate fn print_const(cx: &DocContext<'_>, n: &'tcx ty::Const<'_>) -> String {
     match n.val {
         ty::ConstKind::Unevaluated(def, _, promoted) => {